‹‹‹ Vitr. 8.3.1 | Table of Contents | Vitr. 8.3.3 ›››
2There are also cold springs whose smell and taste are bad. These arise in the lower subterranean places, then pass through hot districts, and afterwards continuing their course for a considerable distance, are cold when they rise to the surface, and of a vitiated taste, smell, and colour. Such is the river Albula, in the Tiburtine way: such are the cold fountains in the lands of Ardea, both of a similar smell, which is like sulphur: such, also, are found in other places. But these, though cold, seem, nevertheless, to boil: for, falling from a high place on to a heated soil, and acted on by the meeting of the water and fire, they rush together with great violence and noise; and, apparently inflated by the violence of the compressed air, they issue boiling from the spring. Among them, however, those whose course is not open, but obstructed by stones or other impediments, are, by the force of the air through the narrow pores driven up to the tops of hills.
2And there are some cold springs that have a bad smell and taste. They rise deep down in the lower strata, cross places which are on fire, and then are cooled by running a long distance through the earth, coming out above ground with their taste, smell, and colour spoiled; as, for instance, the river Albula on the road to Tivoli and the cold springs of Ardea, which have the same smell and are called sulphur springs, and others in similar places. Although they are cold, yet at first sight they seem to be hot for the reason that when they happen upon a burning spot deep down below, the liquid and the fire meet, and with a great noise at the collision they take in strong currents of air, and thus, swollen by a quantity of compressed wind, they come out at the springs in a constant state of ebullition. When such springs are not open but confined by rocks, the force of the air in them drives them up through the narrow fissures to the summits of hills.